Ultrasonographic and radiographic features of a true gastrogastric intussusception with spontaneous resolution in a cat

Abstract An 11‐year‐old, female spayed, domestic shorthair cat with a 1‐week history of vomiting was diagnosed with a gastrogastric intussusception using ultrasound. Distinguishing ultrasonographic findings included invagination of the gastric fundus into the body and were correlated to radiographs acquired at the time of the evaluation. Spontaneous resolution of the gastrogastric intussusception was observed on a positive‐contrast upper gastrointestinal fluoroscopic study done the following day. Due to worsening comorbidities, which most significantly included chronic renal disease and pancreatitis, and declining quality of life, the patient was humanely euthanized 10 months later. Necropsy revealed no gross and histopathologic abnormalities associated with the stomach. A definitive cause for the intussusception remains unknown.


INTRODUCTION
As previously defined, in contrast to pylorogastric or duodenogastric intussusceptions, true gastrogastric intussusceptions represent invagination of the gastric fundus into the lumen of the gastric body (Graham et al., 2020;Vikram et al., 2006). This finding has been rarely reported in human literature and is predominantly diagnosed in older human patients (greater than 65 years of age), while only young dogs are affected in the very few available peer-reviewed veterinary publications (Behrooz & Cleasby, 2018;Graham et al., 2020;Testault et al., 2022;Vikram et al., 2006). The current report describes a similar finding in a mature cat, suggesting that a different age distribution may exist between species. A report by Testault et al. (2022)  found a bimodal age distribution, which also differs from reports of young dogs being more commonly affected. Feline intussusceptions are prevalently enteroenteric, more often reported to be jejunojejunal and ileocolic, and rarely involve the stomach (Burkitt et al., 2009;Levitt & Bauer, 1992). In the absence of identifiable cause, intussusceptions in young cats are more commonly considered idiopathic, while neoplasia is a more prevalent reported aetiology in older cats (Burkitt et al., 2009;Levitt & Bauer, 1992). Comorbidities are not uncommon but diverse with an undetermined predisposing role in the formation of intussusceptions in cats (Burkitt et al., 2009). Cats most often present with signs of lethargy and anorexia of a variable duration, ranging between 1 day to 1 month (Burkitt et al., 2009;Levitt & Bauer, 1992;Patsikas et al., 2003). Vomiting is seen less commonly with an inconsistent incidence reported in the literature (Burkitt et al., 2009;Vet Med Sci. 2022;8:2251-2255 wileyonlinelibrary.com/journal/vms3 2251 Patsikas et al., 2003). A higher frequency of intussusceptions is described in Maine Coons (Haider et al., 2019). A predisposing cause in this population of cats remains unknown (Haider et al., 2019;Verschoof et al., 2015). Intussusceptions involving the stomach are rarely reported in cats and are primarily gastroesophageal intussusceptions in a few case reports (Martinez et al., 2001;Tayler et al., 2021). In dogs, gastroesophageal, gastrogastric and gastroduodenal intussusceptions are described. True gastrogastric intussusceptions are the less frequently reported type. A distinct aetiology remains unknown; although a most recent report describes a benign polyp and gastritis as a possible cause. A similar disease has not been previously described in cat, making this case report the first description of a gastrogastric intussusception in a feline patient. reference interval 0.1-0.3 g/dl), and neutrophilia (11.0 × 10 3 neutrophils/µl; reference interval 2.3-9.8 neutrophils/µl

DISCUSSION
To the authors' knowledge, this report represents the first documented case of a true gastrogastric intussusception in a cat. The clinical signs of the cat in the current report were acute, lasting a few days, and differentiated from the shorter duration (<24 h) of the acute clinical signs of vomiting and hematemesis described in dogs and did not include the clinical signs of abdominal pain and weight loss described in human patients (Behrooz & Cleasby, 2018;Graham et al., 2020;Vikram et al., 2006). Additionally, the reported dogs had no prior history of vomiting, unlike the cat in this report, and acute relapse of the intermittent mild vomiting episodes was also considered (Graham et al., 2020;Testault et al., 2022). Chronic intermittent clinical signs of vomiting in a dog are also reported in a small case series (Testault et al., 2022). The primary concern of vomiting in the cat differed from the more prevalent signs of lethargy and anorexia reported in cats with intussusception (Burkitt et al., 2009;Patsikas et al., 2003). The gastrogastric intussusception was considered self-resolved since additional imaging failed to support persistence or recurrence of the gastrogastric intussusception.
Self-resolution of pylorogastric intussusceptions of unknown aetiology has been described in dogs (de Brito Galvao et al., 2011;Huml et al., 1992). The patient's clinical signs persisted following resolution of the intussusception and resolved following transition to a canned diet formulation alone. While it is possible that the intussusception caused the vomiting and apparent intolerance for dry kibble, it is also possible that the vomiting occurred secondary to other comorbidities such as diet-responsive enteropathy or pancreatitis.
Radiographs and ultrasound were useful imaging modalities for the diagnosis of true gastrogastric intussusception in cats. On radiographs, atypical distribution of intraluminal gas within the stomach and the presence of a soft tissue opaque bulge in the region of the gastric body, fundus, and/or cardia may raise suspicion for a gastrogastric intussusception. Ultrasonography helped confirm the presence of, and further characterize the gastrogastric intussusception, as well as identify comorbidities. Alternatively, CT has been described as a useful imaging modality for the identification of true gastrogastric intussusception in dogs (Graham et al., 2020).
True gastrogastric intussusceptions in older human patients are most commonly associated with benign and malignant gastric tumours (Graham et al., 2020;Huml et al., 1992;Vikram et al., 2006) reported canine case of gastrogastric intussusceptions and has previously been described as a sequela of pancreatitis in dogs (Graham et al., 2020;Murakami et al., 2019;Testault et al., 2022). While the ultrasonographic features of the current case did not support a diagnosis of gastric wall oedema, the presence of pancreatitis and evidence of chronic portal hypertension on histopathology did not rule out the possibility of imperceptible gastric wall oedema at the time of diagnosis. Gastric wall oedema was identified on histopathology in one of the canine cases; however, this finding was considered likely secondary to compromised venous and lymphatic return (Graham et al., 2020).
Furthermore, portal hypertension has previously been postulated as a cause for gastrogastric intussusception in the human literature in the absence of a tumour and may be a considered cause for the gastrogastric intussusception in the reported feline patient (Behrooz & Cleasby, 2018 In conclusion, this is the first case report of a true gastrogastric intussusception in cat. Ultrasound and radiographs were useful modalities for the diagnosis of the true gastrogastric intussusception in the current case and shared imaging characteristics similar to prior veterinary reports. The gastrogastric intussusception spontaneously resolved and additional imaging failed to support recurrence. A cause for the true gastrogastric intussusception in this cat remained uncertain. The patient's clinical decline leading and ensuing euthanasia at a later time was deemed unrelated to any gastric pathology.

ACKNOWLEDGEMENT
We would like to thank all co-authors for their support in the realization of this case report.

CONFLICTS OF INTEREST
The authors declare no conflict of interest.

FUNDING INFORMATION
None.

ETHICS STATEMENT
Approval from the Ethics Committee was not needed for the completion of this case report.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.